JP3280563B2 - Discharge lamp lighting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting circuit for performing power control so as to supply power exceeding its rated power and then shift to constant power control when the discharge lamp is turned on.

[0002]

2. Description of the Related Art In recent years, a small discharge lamp (for example, a metal halide lamp) has been attracting attention as a light source instead of an incandescent lamp. For example, a DC power supply, a DC power supply circuit, and a DC-AC converter have been used as a configuration of the lighting circuit. A device provided with a circuit, a starting circuit, and the like is known.

[0003] In order to shorten the starting time and restarting time of the discharge lamp, the arc tube is rapidly warmed by supplying power exceeding its rated power at the initial stage of lighting of the discharge lamp.
Methods for enhancing luminescence are known.

However, when the power supplied to the discharge lamp is rapidly changed, the overshoot and undershoot become remarkable in the change of the luminous flux of the discharge lamp, and the luminous flux fluctuates greatly, so that the luminous flux of the discharge lamp is stabilized. There is a problem that it is difficult to reduce the time required for the process.

[0005] Therefore, in the transition from the control of supplying power exceeding the rated power of the discharge lamp at the initial stage of lighting of the discharge lamp (hereinafter referred to as "light emission promotion control") to the constant power control at the rated power of the discharge lamp. In addition, a circuit configured to gradually reduce the power supplied to the discharge lamp with the passage of time and to finally perform power control so that the supplied power becomes the rated power can be considered.

[0006]

However, the state of the discharge lamp at the time of lighting is not always the same state. When the discharge lamp is lit while the arc tube is cooled (hereinafter referred to as "cold start"). ), When the discharge lamp is turned on while the arc tube after the discharge lamp is turned off is still hot (hereinafter, referred to as "hot start"), or between the two.

Therefore, in a circuit in which the rate of reduction of the power supplied to the discharge lamp is fixed to a certain value at the time of transition from the light emission promotion control to the constant power control, undershoot or overshoot in the temporal change of the luminous flux of the discharge lamp is required. There is a problem that it is difficult to reduce shoots.

That is, even if the reduction rate of the supplied power is set to a certain value and a luminous flux change which does not cause any problem at the time of a cold start is obtained, the set value of the reduction rate does not always apply to the control at the time of a hot start. .

Therefore, the state of the discharge lamp at the time of lighting (that is,
It is conceivable to control the power supply to the discharge lamp separately by determining whether it is a cold start, a hot start or an intermediate state between the two), but if a control circuit is provided separately for each state, the circuit configuration Is complicated.

An object of the present invention is to control the power of a discharge lamp so that the luminous flux of the discharge lamp quickly reaches a rated luminous flux without complicating the circuit configuration.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a discharge lamp lighting circuit for supplying power to a discharge lamp exceeding its rated power and then shifting to constant power control of the discharge lamp. Has a plurality of time-constant circuits having different time constants or a time-constant circuit having an order of second or higher, and the time constant changes over time, and accordingly, the discharge lamp The power control is performed so that the rate of decrease in the power supplied to the power supply changes, and the transition period to the constant power control is divided into a plurality of periods. Is specified to be a larger value. Furthermore, the discharge lamp run
Voltage and / or lamp current or their corresponding signals
Detection means to obtain the
Discharge lamp by adding the output of the transition control means
Is generated to generate the power control signal.

Thus, according to the present invention, the transition control means can change the reduction rate of the power supplied to the discharge lamp with time by a combination of a plurality of time constants.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS.

FIG. 1 shows the configuration of a discharge lamp lighting circuit 1 according to the present invention, which includes a power supply 2, lighting control means 3, lamp voltage / current detection means 4, and power control means 5.

The lighting control means 3 is provided for controlling lighting of the discharge lamp 6 based on an AC or DC power supply voltage supplied from the power supply 2, and its output is a control signal from the power control means 5. Is controlled by The lighting control means 3 includes a starting circuit for generating a starting pulse at the beginning of lighting of the discharge lamp 6 to start the discharge lamp 6.

The lamp voltage / current detecting means 4 outputs the lamp voltage or lamp current supplied from the lighting control means 3 to the discharge lamp 6 or a signal corresponding thereto.
It is provided in order to obtain a voltage value or a current value detected inside, and sends the detection result to the power control means 5.

The power control means 5 has a light emission promotion control means 7, a shift control means 8, and a constant power control means 9 as its control functions as shown in the figure. It is to be noted that these control means are not necessarily provided as separate circuits, but only have a configuration as illustrated when the functional control sections of the power control means 5 are visualized by block elements. Be careful.

The light emission promotion control means 7 controls the light emission of the discharge lamp 6 at the initial stage of the lighting of the discharge lamp 6 by supplying a power exceeding the rated power so as to promote the light emission of the discharge lamp and to improve the time rise characteristics of the luminous flux. In addition, the constant power control means 9 guarantees stable lighting by performing constant power control at the rated power during steady lighting of the discharge lamp.

The transition control means 8 operates in a transitional state from when the discharge lamp 6 is placed under the control of the light emission promotion control means 7 to when the discharge lamp 6 is placed under the control of the constant power control means 9. It is responsible for power control, and gradually reduces the power supplied to the discharge lamp 6 over time, and has a plurality of time constant circuits for that purpose.

In FIG. 2, the horizontal axis represents time t, and the vertical axis represents a power control signal (hereinafter referred to as “W”) for controlling the power supplied to the discharge lamp 6.
P ”. ) And a detection signal of the lamp voltage of the discharge lamp 6 (this is referred to as “VS”), and shows a signal change at the time of a cold start of the discharge lamp.

As shown in the figure, the power supplied to the discharge lamp 6 is large during the period t1 in which the discharge lamp 6 is under the control of the light emission promotion control means 7, and the power supplied to the discharge lamp 6 is controlled in the time t2 in the period t2 under the control of the transition control means 8. Gradually decreases over time,
In a period t3 under the control of the constant power control means 9, the control value reaches the control value indicating the rated power (this is referred to as "WPc"), and the control is stabilized. Note that the detection signal VS shows a relatively low value at the beginning of the period t1, and then gradually rises as time elapses, and then gradually approaches a steady value. In addition, period t2
Is larger than the power supplied to the discharge lamp in the period t3, the period t1 and the period t2
Can be considered as a period for promoting light emission of the discharge lamp, and t2 can be regarded as a latter period of the period.

In FIG. 3, the horizontal axis represents time t, and the vertical axis represents the power control signal WP and the lamp voltage detection signal VS, and shows the signal change at the time of hot start of the discharge lamp.

As shown in the figure, in this case, the excessive power supply to the discharge lamp by the light emission promotion control means 7 is performed for a short time or is not performed, and the discharge lamp 6 is immediately turned on by the transition control means 8. Under the control, the power control signal WP gradually decreases over time from a value slightly larger than the control value WPc, and then reaches WPc to stabilize the control. The lamp voltage detection signal VS immediately rises from a relatively high value to a steady value.

By the way, it is conceivable to use one time constant circuit to regulate the time change rate of the power supply by the transition control means 8. In this case, control of the discharge lamp is performed by the light emission promotion control means 7 by the transition control means. The power control signal WP gradually decreases with a certain time constant with the passage of time from the point when the process shifts to the means 8, and finally settles at WPc.

However, it is difficult to set one time constant so as to obtain a good luminous flux rising characteristic at the time of a cold start, a hot start, or a lighting start in an intermediate state between the two. It is.

FIG. 4 shows an example of the temporal change of the luminous flux of the discharge lamp (this is referred to as "L"). When a set value having a time constant is adopted, the graph curve gc shows an exaggerated graph. In such a case, a large undershoot may occur in the light beam L at the time of the cold start, or a large overshoot may occur in the light beam L at the time of the hot start as exaggeratedly shown in the graph curve gh.

In view of this, it is conceivable to employ a circuit configuration that detects the state of the discharge lamp when it is turned on and changes the rate of decrease in the power supplied by the transition control means 8 according to the detection result. Is inevitable.

According to the present invention, the period t
The power supply is appropriately supplied to the discharge lamp by temporally changing the reduction rate of the power supply in the step (2). That is, for example, as shown in FIG. 5, the transition control means 8 according to the present invention includes a plurality of time constant circuits 10a having different time constants,
10b,..., And these time constant circuits are sequentially operated as the supply power decreases in the transition period t2, so that the time constant corresponding to the reduction rate of the supply power changes. Is done.

For example, assuming that the transition period t2 is divided into two periods, the time constant is set to a small value in the first half to reduce the overshoot at the time of hot start, and the time constant is set to a large value in the second half. It is possible to set a time constant such as to reduce the undershoot at the time of cold start, and more generally, to set the transition period t2 to a plurality of periods (the lengths of the periods are not necessarily equal). When the discharge lamp is lit from an intermediate state between cold start and hot start, depending on the combination of such time constants, the value of the time constant in each period can be set separately. In addition, it is possible to appropriately control the reduction rate of the supplied power during the transition period. Note that instead of providing a plurality of time constant circuits having different time constants, the transition control means 8 can be constituted by a time constant circuit having an order of 2 or more.

Thus, when the design of the transition control means 8 is changed, it is only necessary to add a time constant circuit or to increase the order (for example, to make the primary time constant circuit a secondary configuration, etc.). Therefore, this does not significantly complicate the circuit configuration.

In generating the power control signal WP as shown in FIGS. 2 and 3, the configuration of the time constant circuit is as follows.
Configuration using only passive elements (resistance and capacitor),
Although an integration circuit configuration using passive elements and active elements can be used, the former is in line with the gist of the present invention in that the circuit configuration is simplified.

[0032]

6 to 9 show an embodiment of the present invention.

In the lighting circuit 11 shown in FIG. 6, a battery 12 corresponding to the power supply 2 has input terminals 13 and 13 '.
And a lighting switch 14 is provided on one of the power supply lines.

The battery voltage is supplied to a DC power supply circuit 15, where the voltage is increased and / or decreased.

The DC-AC conversion circuit 16 is a DC power supply circuit 1
5 is converted into an AC voltage. For example, a bridge-type circuit including a plurality of pairs of semiconductor switch elements arranged on a power supply path to a discharge lamp and a configuration including a drive control circuit thereof are included. Although any configuration can be used for the DC-AC conversion circuit 16, any configuration for converting a DC voltage into a sine wave voltage, a rectangular wave voltage, or the like can be used.

The igniter circuit 17 arranged at the subsequent stage of the DC-AC conversion circuit 16 generates a starting pulse for the discharge lamp 18 and superimposes it on the output of the DC-AC conversion circuit 16, and then outputs an AC output terminal 19. And a circuit for applying a voltage to the discharge lamp 18 connected between the discharge lamp 18 and 19 '.

DC power supply circuit 15 and DC-AC conversion circuit 1
A detection means for detecting the output voltage or output current of the DC power supply circuit 15 is provided between the DC power supply circuit 6 and the DC power supply circuit 6. , 20 '. Also,
The current detecting resistor 21 for detecting the output current of the DC power supply circuit 15 is connected to the DC power supply circuit 15 and the DC-AC conversion circuit 1.
6 is arranged on one of the connection lines.

Detection signals from the resistors 20, 20 'and the current detecting resistor 21 are sent to a control circuit 22, and the control circuit 2
2 generates a power control signal corresponding to these detection signals and sends it to the DC power supply circuit 15 to control its output voltage. For example, at the time of cold start of the discharge lamp 18, the power supply exceeding its rated power is performed to promote light emission, and then the power supplied to the discharge lamp 18 is reduced at a reduction rate specified by a time constant circuit to perform constant power control. Or control for stably lighting the discharge lamp 18 by constant power control.

The control circuit 22 realizes the function of the power control means 5 and includes a light emission promotion control circuit, a constant power control circuit, and a transition control circuit. The transition control circuit uses a capacitor and a resistor. It is composed of a time constant circuit. The light emission promotion control circuit has, for example, a configuration in which the output current of the DC power supply circuit 15 is detected and the power supply value to the discharge lamp 18 is controlled in accordance with the level. By controlling the level of each detection signal related to the output voltage and the output current of the DC power supply circuit 15 at a certain ratio to be constant, a control line obtained by linear approximation to a constant power curve is obtained. A configuration or the like for performing the power control according to the above can be cited, but the configuration thereof does not matter and the description is omitted.

FIG. 7 shows a configuration example 23 of a main part of the control circuit 22. The detection voltage (ie, voltage division by the resistors 20, 20 ') relating to the output voltage Vdc of the DC power supply circuit 15
Is input to an inverting input terminal of an operational amplifier 25 via a resistor 24, and a predetermined reference voltage (referred to as “E1”) indicated by a constant voltage power supply 26 is supplied to a non-inverting input terminal. A resistor 27 is interposed between the inverting input terminal and the output terminal of the operational amplifier 25.

The operational amplifier 28 and the diode 29 constitute a buffer 30, and the non-inverting input terminal of the operational amplifier 28 is connected to the output terminal of the operational amplifier 25. The output terminal of the operational amplifier 28 is connected to the anode of the diode 29, and the cathode of the diode 29 is connected to the non-inverting input terminal of the operational amplifier 28 and to the output terminal 31.

The transition control circuit 22a is provided in parallel with the buffer 30, one end of a capacitor 32 is connected to the output terminal 31, and the other end is a constant voltage source 33 (the voltage value is "E2"). )It is connected to the. A series circuit of a resistor 34 and a capacitor 35 is provided in parallel with the capacitor 32, and a resistor 36
Are connected in parallel, and a resistor 3 is connected to the resistor 36.
7 and a series circuit of the Zener diode 38 are connected in parallel. The capacitance of the capacitor 35 is set to a smaller value than the capacitance of the capacitor 32.

The signal obtained from the output terminal 31 corresponds to a part of the above-described power control signal WP, and the signal is processed directly or in a process necessary for control (for example, in a control using pulse width modulation, After being converted into a cycle, etc.).

Thus, in the circuit 23 described above,
The power control signal can be easily obtained by adding the output of the transition control circuit 22a to the signal obtained by inverting and amplifying the detection signal of Vdc corresponding to the lamp voltage of the discharge lamp 18 by the operational amplifier 25. Becomes easier.

FIG. 8 shows an example of a change in light flux at the time of a cold start, with time t taken on the horizontal axis and light flux L of the discharge lamp 18 taken on the vertical axis. The period “ta” indicates the initial stage of the rising of the light beam L, the period “tb” indicates the first half of the transient period following the period ta, and the period “tc” indicates the second half of the transient period following the period tb. The steady lighting period of the electric lamp 18 is shown.

In the period ta, since the lamp voltage of the discharge lamp 18 is low, the capacitor 32 of the transition control circuit 22a is rapidly charged, and the luminous flux L rises quickly. In the period tb, the capacitor 32 is discharged through the resistor 36 and the capacitor 35 is charged through the resistor 34, so that the resistance values of these resistors and the capacitors 32, 3
Discharge lamp 1 according to the time constant defined by the capacitance of
8 is defined.

In the period tc, the capacitor 35 is discharged via the resistors 34 and 36, and the power supplied to the discharge lamp 18 is determined by the time constant defined by the resistance of these resistors and the capacitance of the capacitor 35. Is defined. By setting the time constant to delay the decrease in the power supplied to the discharge lamp 18, the undershoot of the light beam L during the period tc (this is exaggerated as "ud" in FIG. 8) is suppressed. be able to.

FIG. 9 shows an example of a change in light flux at the time of hot start, with time t on the horizontal axis and light flux L of the discharge lamp 18 on the vertical axis. Note that the periods ta to td are as described above.

In this case, the period ta is very short, and the light flux L rises with a slight fluctuation. During the period tb, the capacitor 32 is discharged through the resistor 36 and the capacitor 35 is charged through the resistor 34, so that the time constant defined by the resistance values of these resistors and the capacitance of the capacitors 32, 35 This defines the rate of decrease in the power supplied to the discharge lamp 18. It should be noted that the overshoot of the light beam L during the period tb (this is exaggerated as “ov” in FIG. 9) is suppressed by setting the time constant to accelerate the decrease in the power supplied to the discharge lamp 18. be able to.

In the period tc, the capacitor 35 is discharged via the resistors 34 and 36, and the power supplied to the discharge lamp 18 is determined by the time constant defined by the resistance values of these resistors and the capacitance of the capacitor 35. Is defined.

When the discharge lamp is lit in an intermediate state between the cold start and the hot start, only the lengths of the periods ta, tb, tc and the rise of the light flux L are different.

In this embodiment, the output of the transition control circuit 22a is added to the circuits (20, 20 ', 24 to 27) relating to the detection of the lamp voltage. However, the present invention is not limited to this. Can be adopted in which the output of the transition control circuit 22a is added to the circuit related to the detection of. Further, in the configuration of the transition control circuit 22a, a time constant circuit is formed by connecting a plurality of capacitors (32, 35) in parallel (this allows the use of a capacitor having a small capacitance, thereby reducing costs and miniaturization. However, various embodiments are possible, such as connecting a plurality of capacitors in series or replacing the Zener diode 38 with a diode.

[0053]

As is apparent from the above description, according to the first aspect of the present invention, the transition control means reduces the rate of reduction of the power supplied to the discharge lamp in time by a combination of a plurality of time constants. Since it can be changed, it is not necessary to determine the lighting state of the discharge lamp and separately control the power supplied to the discharge lamp, and the addition of a time constant circuit or a change in the order changes the luminous flux of the discharge lamp significantly. By performing power control so that overshoot and undershoot do not occur, the start time and restart time of the discharge lamp can be reduced. And the lamp voltage and / or run of the discharge lamp.
Detecting means for obtaining the loop currents or their equivalent signals
By adding the output of the transition control means to the output of
It is possible to easily obtain a power control signal for an electric lamp.

According to the second aspect of the present invention, the discharge lamp is switched to the discharge lamp in the first half and the second half of the transition period in which the state in which the power exceeding the rated power is supplied to the discharge lamp is shifted to the constant power control of the discharge lamp. By changing the reduction rate of the supplied power, the rising characteristics of the luminous flux of the discharge lamp can be easily controlled.

[0055]

[0056]

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an outline of a configuration of a discharge lamp lighting circuit of the present invention.

FIG. 2 is a diagram for describing a temporal change of a power control signal at the time of a cold start.

FIG. 3 is a diagram for describing a temporal change of a power control signal at the time of a hot start.

FIG. 4 is a diagram for explaining a change in luminous flux of a discharge lamp and a rising characteristic thereof.

FIG. 5 is a diagram showing a configuration of a transition control unit.

6 shows an embodiment of the present invention together with FIGS. 7 to 9, and is a circuit block diagram showing an outline of a lighting circuit. FIG.

FIG. 7 is a circuit diagram illustrating a configuration example of a main part of a control circuit.

FIG. 8 is a diagram showing an example of a change in the luminous flux of the discharge lamp at the time of a cold start.

FIG. 9 is a diagram showing an example of a change in the luminous flux of the discharge lamp at the time of a hot start.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge lamp lighting circuit, 4 ... Detection means , 5 ... Power control means, 6 ... Discharge lamp, 8 ... Transition control means, 10a, 10b ...
Time constant circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-98295 (JP, A) JP-A-7-45390 (JP, A) JP-A 8-8087 (JP, A) 82799 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 41/14-41/298

Claims (2)

(57) [Claims] When the discharge lamp is turned on after the discharge lamp has been cooled, the power supplied to the discharge lamp exceeds its rated power, and the power supplied to the discharge lamp is reduced.
In a discharge lamp lighting circuit having a power control means for controlling a transition to a constant power control of a discharge lamp, (a) a power supply exceeding a rated power to the discharge lamp is performed, and then the discharge lamp is controlled to a constant power control. The shift control means for shifting has a plurality of time constant circuits having different time constants or a time constant circuit having an order of second or higher, and the time constant changes with time, and (B) The transition period to the constant power control is divided into a plurality of periods, and the time constant is in a later period than in the first period of the transition period. (C) the lamp voltage and / or lamp current of the discharge lamp
Is to provide detection means to obtain those equivalent signals
The output of the above transition control means is added to the output
To generate a power control signal for the discharge lamp.
And a discharge lamp lighting circuit. 2. The discharge lamp lighting circuit according to claim 1, wherein the transition control means includes two time constant circuits having different time constants.
The following time constant circuit is provided, and during the transition period of the discharge lamp to the steady state, the reduction rate of the power supplied to the discharge lamp in the first period is defined by the setting of the first time constant. The reduction rate of the power supplied to the discharge lamp is defined by setting a second time constant, and the second time constant is defined to be a value larger than the first time constant. Discharge lamp lighting circuit.